Determining polygon intersection and containment

Question

I have a set of simple (no holes, no self-intersections) polygons, and I need to check that they don\'t intersect each other (one can be entirely contained in another; that is o

Answer 1

To test for intersections you could use my freeware clipper library: http://sourceforge.net/projects/polyclipping/ .

To test for containment, first exclude intersections as above. Then use Clipper again adding all the polygons - Clipper.AddPolygon(). Then perform a Union (boolean OR) operation on the polygons - Clipper.Execute(ctUnion, solution). If the Clipper.ForceAlternateOrientation property is true, Clipper will return in the solution outer polygons in clockwise orientation and contained polygons (holes) in counter-clockwise orientation. It should then be a simple matter of testing polygon orientations and applying a PointInPolygon from one vertex in a counter-clockwise polygon against the other clockwise polygons.